• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.1064-1067
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• 2004

The aim of this paper is to develop a GUI based software that can predict the flow and noise generated by fan. This user-friendly software is designed for the usual fan user in the various industrial companies as well as researcher related to rotating blade:;. Software consists of 3-modules; (1) concept design and performance prediction module using simple and fast methods, (2) preliminary design and flow/noise prediction module using free-wake potential solver and acoustic analogy and (3) detail design module using accurate CFD-software and acoustic formula. Some validations and applications in various fields are described.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.128-132
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• 2008

The noise levels and individual employee noise exposure levels within a factory will determine the need for hearing conservation program. The difficulty in not having an effective hearing conservation program is the risk of hearing loss that employees may sustain. In the last few years the claims for hearing loss compensation have grown due to class action litigation brought against the employer and companies that have equipment in the factory alleged to have caused hearing loss. The Blower in the factory generates the noise of 98.3dB(A) in the frequency range of 2,000Hz, which may cause occupational hearing loss. By designing close type enclosures which are made of absorption material, about 24.4dB(A) reduction has been in the factory. It is demonstrated that this kind of enclosures can be effectively used to reduce the noise in the factory.

• International Journal of Railway
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• v.6 no.3
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• pp.120-124
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• 2013

The aim of this study was to clarify the characteristics of interior noise in Japanese, Korean, and Chinese subways. The octave-band noise levels, A-weighted equivalent continuous sound pressure level ($L_{Aeq}$) and parameters extracted from interaural cross-correlation/autocorrelation functions (ACF/IACFs) were analyzed to evaluate the noise inside running train cars quantitatively and qualitatively. The average $L_{Aeq}$ was 72-83 dBA. The IACF/ACF parameters of the noise showed variations in their values, suggesting they are affected by the characteristics of the trains running, wheel-rail interaction, and cross-section of the tunnels.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.406-410
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• 2005

The wind turbine, Europe and the United States are different with the standards process each other when the manufacturing company which in order to demand the standards process to a construction in the multi country with interested parties of the corresponding nation to, always the re-agreement is difficult. Korean wind turbine also detail there is not a standard, when it produces and establishes of wind turbine, the problem point occurs. It is like that investigation of international standards system it leads and when it prepares the Acoustic noise measurement of the Wind Turbine Systems of Korea, it prepares the base for industrial development wind turbine of Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6284-6289
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• 2013

With the application of k-space trajectory in a different manner and analyzing the influence of noise and its direction, this study was conducted to obtain high-quality images with minimal influence of noise during an MRI examination for cerebrovascular disease, which has a low signal for imaging. To evaluate influence of the noise of different k-space trajectories, a linear Cartesian coordination trajectory and non-Cartesian coordination trajectory were applied to 38 people who had received a high-resolution MRI examination for the early detection of cerebrovascular disease. As a result, the non-Cartesian coordination trajectory showed a 43.32% lower signal of lumens in the internal carotid artery than a linear Cartesian coordination trajectory, and the noise level was also 50.19% lower in a non-Cartesian coordination trajectory. This result shows that noise occurs less in a non-Cartesian coordination trajectory than a linear Cartesian coordination trajectory, and a non-Cartesian coordination trajectory is more effective in low-signal and low-resolution MRI examination. Therefore, when performing high-resolution MRI examination with a low-signal cerebrovascular system, the use of non-Cartesian coordination k-space trajectory will minimize the influence of noise and provide good images.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2068-2072
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• 1997

Acoustic noise has become an increasingly important issue, especially in the industrial environment. Nowadays home and office are not exceptional, mainly due to the increase in the usage of machinery. Active Noise Control(ANC) becomes efficiently an available tool for the noise suppression with rapid advances of solid state electronics. In this study an ANC system is developed for audio headphone to work as a noise protector, so called an ear-muff. The system is developed to kill a certain frequency band noises selectively which is purposed to suppress only the dominant ambient noise such that normal numan conversation is not disturbed with wearing the ear-muff. For the purpose, an ANC design strategy is suggested and implemented with an analogue control circuit. The performance is evaluated by frequency response test, which shows well consistence with theoretical one. The results are so satisfactory that noise of 640 Hz, which is aimed to suppress, is reduced by 20db without significant distortion in other frequency band.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1416-1421
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• 2013

In this paper, the Euclidean distance between the probability density functions (PDFs) for biased errors and a Dirac-delta function located at zero on the error axis is proposed as a new performance criterion for adaptive systems in non-Gaussian noise environments. Also, based on the proposed performance criterion, a supervised adaptive algorithm is derived and applied to adaptive equalization in the shallow-water communication channel distorted by severe multipath fading, impulsive and DC-bias noise. The simulation results compared with the performance of the existing MEDE algorithm show that the proposed algorithm yields over 5 dB of MSE enhancement and the capability of relocating the mean of the error PDF to zero on the error axis.

• Journal of Information Processing Systems
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• v.16 no.3
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• pp.530-540
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• 2020

In order to solve the problem of low tracking accuracy caused by complex noise in the fault diagnosis of complex nonlinear system, a fault diagnosis method of high precision cost reference particle filter (CRPF) is proposed. By optimizing the low confidence particles to replace the resampling process, this paper improved the problem of sample impoverishment caused by the sample updating based on risk and cost of CRPF algorithm. This paper attempts to improve the accuracy of state estimation from the essential level of obtaining samples. Then, we study the correlation between the current observation value and the prior state. By adjusting the density variance of state transitions adaptively, the adaptive ability of the algorithm to the complex noises can be enhanced, which is expected to improve the accuracy of fault state tracking. Through the simulation analysis of a fuel unit fault diagnosis, the results show that the accuracy of the algorithm has been improved obviously under the background of complex noise.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3647-3653
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• 2012

In active noise control filter, IIR filter structure which used for control filter assures the stability property. The stability characteristics of IIR filter structure is mainly determined by pole location of control filter within unit disc, so stable selection of the value of control filter coefficient is very important. In this paper, we proposed novel adaptive stabilized Filtered_U LMS algorithms with IIR filter structure which has better convergence speed and less computational burden than conventional FIR structures, for multi-channel active noise control with vehicle enclosure signal case. For better convergence speed in adaptive algorithms, fuzzy LMS algorithms where convergence coefficient computed by a fuzzy PI type controller was proposed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.568-575
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• 2022

This paper is a study on frequency analysis and electronic noise reduction of energy storage system (ESS). We acquired 4 necessary data for about 2 minutes and 4 seconds using a sampling frequency of 10,000 Hz in ESS. Fast Fourier transform (FFT) was used for electronic noise analysis from the acquired data. As a result, it was confirmed that DC component, fundamental wave, second and higher harmonic component exist. For the attenuation of harmonics, low-pass filter (LPF) was applied. We confirmed that an attenuation of approximately 59.3% appears from the second harmonic. The presence of many harmonic components in the data of the ESS was expected to occur due to the insufficiency of optimization among the modules inside the ESS. Therefore, we propose that a national certification system for ESS should be introduced to settle down the issue properly.